Metal and plastic power supply chains are well known for supporting one or more power supply conduits or lines, such as electrical cables, fluid power hoses and the like, between a fixed position and a relatively movable position where the power supply chain is connected to a power consumer, such as movable machinery which can comprise, for example, a gantry or other crane, elevator, machine tool slide, robot, etc. The power supply chain typically is connected by brackets to a tow arm of the movable power consumer such that the chain is pulled or pushed at the bracket connection in order to effect chain travel with the power consumer.
In some service applications involving light-weight, plastic power supply chains where the chain is required to travel through an extended travel stroke to provide power to the relatively movable consumer, the dynamic portion of the power supply chain is designed to sag downwardly when the self-supporting travel distance of the chain is exceeded. The sagging portion of the power supply chain is supported atop the static portion of the chain residing on a support, such as on the bottom of a guide tray, and frictionally slides over the static portion of the chain during the travel stroke of the power consumer. The dynamic portion of the power supply chain typically is supported on the static portion of the chain in the guide tray in frictional contact therewith during a substantial portion of the total travel stroke of the movable power consumer. For illustration purposes, for a total travel stroke of the power consumer of 50 feet, frictional engagement between the dynamic and static chain portions can occur over 35 feet of travel, while for a total travel stroke of the power consumer of 300 feet, frictional engagement between the dynamic and static chain portions can occur over 285 feet of travel. In such power supply cable systems, the frictional sliding contact between the dynamic and static portions of the power supply chain during the stroke of the power consumer causes accelerated wear of the plastic chain components, requiring eventual replacement of worn chain components. Moreover, since the power supply chain is pulled or pushed at the bracket connection to the tow arm of the movable power consumer, the frictional sliding forces between the dynamic and static chains portions substantially increase towing forces on the power supply chain at the bracket connection to the power consumer, adversely affecting movement of the chain and also limiting the travel stroke of the chain.
Still further, in service applications where the power supply chain is received in a guide tray, the frictional resistance between the sagging portion and static portion of the chain when the chain is being returned to a less extended position by power consumer movement can cause upward buckling or upheaval of the dynamic portion of the chain out of the guide tray and possible loss of lateral chain stability wherein the chain buckles upwardly enough to fall to the side out of the guide tray in extreme situations. In the event the power supply chain falls out of the guide tray, the operation of the power consumer must be stopped until the power supply chain is positioned back in the guide tray.
An object of the present invention is to provide apparatus including a power supply chain, power supply chain carriage, and optional guide tray that overcomes the aforementioned disadvantages of previous flexible power supply systems in a manner to reduce wear of the power supply chain components, reduce towing forces at the movable power consumer connected to the power supply chain, and permit an increase of the travel stroke of the power supply chain.